Automatically add CsrfServerLogoutHandler if csrf enabled

The configuration DSL should automatically add CsrfServerLogoutHandler if csrf is enabled

Fixes gh-5337

web/src/test/java/org/springframework/security/web/server/authentication/logout/LogoutWebFilterTests.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2002-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.web.server.authentication.logout;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+import org.springframework.test.util.ReflectionTestUtils;
+
+/**
+ * @author Eric Deandrea
+ * @since  5.1
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class LogoutWebFilterTests {
+	@Mock
+	private ServerLogoutHandler handler1;
+
+	@Mock
+	private ServerLogoutHandler handler2;
+
+	@Mock
+	private ServerLogoutHandler handler3;
+
+	private LogoutWebFilter logoutWebFilter = new LogoutWebFilter();
+
+	@Test
+	public void defaultLogoutHandler() {
+		assertThat(getLogoutHandler())
+				.isNotNull()
+				.isExactlyInstanceOf(SecurityContextServerLogoutHandler.class);
+	}
+
+	@Test
+	public void singleLogoutHandler() {
+		this.logoutWebFilter.setLogoutHandler(this.handler1);
+		this.logoutWebFilter.setLogoutHandler(this.handler2);
+
+		assertThat(getLogoutHandler())
+				.isNotNull()
+				.isInstanceOf(ServerLogoutHandler.class)
+				.isNotInstanceOf(SecurityContextServerLogoutHandler.class)
+				.extracting(ServerLogoutHandler::getClass)
+				.isEqualTo(this.handler2.getClass());
+	}
+
+	@Test
+	public void multipleLogoutHandlers() {
+		this.logoutWebFilter.setLogoutHandler(new DelegatingServerLogoutHandler(this.handler1, this.handler2, this.handler3));
+
+		assertThat(getLogoutHandler())
+				.isNotNull()
+				.isExactlyInstanceOf(DelegatingServerLogoutHandler.class)
+				.extracting(delegatingLogoutHandler -> ((Collection<ServerLogoutHandler>) ReflectionTestUtils.getField(delegatingLogoutHandler, DelegatingServerLogoutHandler.class, "delegates"))
+						.stream()
+						.map(ServerLogoutHandler::getClass)
+						.collect(Collectors.toList()))
+				.isEqualTo(Arrays.asList(this.handler1.getClass(), this.handler2.getClass(), this.handler3.getClass()));
+	}
+
+	private ServerLogoutHandler getLogoutHandler() {
+		return (ServerLogoutHandler) ReflectionTestUtils.getField(this.logoutWebFilter, LogoutWebFilter.class, "logoutHandler");
+	}
+}